226 M. P. Heide-Jorgensen etal. jectively based. The age for change from Acknowledgements grey to white as reported from other areas is fairly similar to what we have seen in This study was supported financially by the Fish- West Greenland (Sergeant 1973; Ognetov eries Directorate of the Greenland Home Rule 1981), but detailed comparisons are not Government and it was conducted by the Green- land Fisheries Research Institute. The beluga possible because the Statistical methods hunters in West Greenland are thanked for pro- used for deriving the mean age at change viding the samples of their harvest. We thank of colour are not specified. However, for Royal Greenland and Greenland Trade Depart- belugas in East Baffin, Brodie (1971) re- ment for help with collection of samples. J.Jen- ported that whitening occurs after 6 and sen, J.Teilmann, F.Thomsen, and RBarner 7 yr in females and males respectively, Neve did the age determinations and the data which is also evident from this study. entry. G.N. Ognetov (SEV-Pinro, Arkhangelsk) kindlymadehisdataonwhitewhaleagefrequen- ciesintheWhite andKaraseasavailable. R M0L- ler Lund and U. Siebert are gratefully acknowl- edged for making tne map and the German translationofthe abstract. Zusammenfassung Alters- und Geschlechtsverteilungvon Belugafängen, Delphinapterus leucas, in Westgrönland und Westrußland Alter und Geschlechtwurden von Belugas oderWeißwalen Delphinapterus teucas, bestimmt, die von 1985-86 und 1989-97 von Eskimos in Westgrönland erlegt wurden. Der Probenumfang umfaßte 712 Weibchen und 596 Männchen. Es gab eine klare Trennung der Wale in der Jagdfischerei, die während des Herbstes in Qaanaaq (früher als Avenersuaq bekannt) und Upernavik, das nördlich des 74°N Breitengrades liegt, stattfindet. Vor allem nicht geschlechtsreife Wale beider Geschlech- ter wurden zusammen mit geschlechtsreifen Weibchen gefangen. Zähne dienten der Altersbestim- mung. Das Alter wurde an Jahreszuwachsringen (GLGs) im Dentin ermittelt unter der Annahme, daß zwei Zuwachsringe pro Jahr entstehen. Mittelwert und Median für Alter nahmen bei beiden Geschlechtern aus Upernavikvon 1985 bis 1994 langsam zu. Sowohl nichtgeschlechtsreife als auch geschlechtsreife Wale wurden in den Überwinterungsgebieten der Disko Bucht und südlich des 70°N Breitengrades entnommen. Die Überlebensrate wurde nach zwei Methoden bestimmt: nach Robson und Chapman (1961) und über den natürlichen Logarithmus des negativen Exponenten einer an die Altersfrequenz angepaßten Kurve. Die Abschätzung der Überlebensrate wurde erschwert durch eine große Anzahlvon Walen, denen bedingt durch eine Abnutzung der Zahnkrone nurein Minima- lalter zugeordnet werden konnte (d.h. keine Neonatlinie im Dentin). Die offensichtliche Überle- bensrate von Belugas vor Westgrönlands wurde auf 0,81 und 0,79 für Weibchen bzw. Männchen geschätzt. Korrekturen dieser Abschätzung für eine beobachtete Bestandsabnahme von 4,7% pro Jahr ergaben eine tatsächliche Überlebensrate von 0,85 und 0,82 für Weibchen bzw. Männchen. Die Schätzwerte dertatsächlichen Überlebensrate sind geringerals die, welche fürdie Belugapopu- lation im Weißen Meer und der Karasee ermittelt wurden, fiirdie Altersdaten aus den 70er und frü- hen 80er Jahren zur Verfügung standen, sowie publizierten Raten für Belugas aus Alaska (1977- 83) miteinervergleichbaren Alterszusammensetzung. Da der Grad der Bejagung in diesen Gebieten wesentlich niedrigerist, bestätigt die geringere Überlebensrate vor Westgrönland deutlich eine Ab- nahme der Population. Der Wechsel in der Hautfärbung von Grau zu Weiß tritt im mittleren Alter von 8,5 und 9,1 Jahren und bei einer mittleren Länge von 367 cm und 445 cm bei Weibchen bzw. Männchen auf. Age and sex distributionsin the catches ofbeLugas 227 References Brodie, P.F. (1971): Areconsideration ofaspects Lowry, L.F.; Burns, J.X; Frost, K.J. (1989): Re- of growth, reproduction, and behavior of the cent harvests of belukha whales, Delphina- white whale (Delphinapterus leucas), with re- pterusleucas,inwestern andnorthernAlaska ference to the Cumberland Sound, Baffin Is- and their potential impact on provisional land, population. J. Fish. Res. Board Can. 28, management Stocks. Rep. Int. Whal. Commn 1309-1318. 39,335-339. Burns, J.J.; Seaman, G.A. (1986): Investigations Ognetov, G.N. (1981): Studies on the ecology of belukha whales in western and northern and the taxonomy of the white whale Alaska. IL Biology and ecology. Fairbanks, (Delphinapterus leucas Pall., 1776) inhabiting Alaska: Report by Alaska Department of the SovietArctic. Rep. Int. Whal. Commn31, FishandGame. 515-520. Doidge,D.W. (1990):Age andstagebasedanaly- Palsb0ll, P.J.; Vader, A.; Bakke, L; El-Gewely, sis of the population dynamics of beluga M.R. (1992): Determination of gender in whales, Delphinapterus leucas, withparticular cetaceans by the Polymerase chain reaction. reference to the Northern Quebec popula- Can.J.Zool.70,2166-2170. tion. Ph.D. thesis McGill University, Mon- Perrin, W.F.; Myrick, A. C. Jr. (1980): Report of treal,Quebec. the Workshop. In: Age determination of DeMaster D.P. (1978): Calculation of the aver- toothed whales and sirenians. Ed. by W.F. age age of sexual maturity in marine mam- Perrin and A. C. Myrick Jr. Rep. Int. Whal. mals.J.Fish.Res.BoardCan.35,912-915. Commn,Spec. Issue3, 1-50. Heide-J0rgensen, M.R; Reeves, R.R. (1996): Robson,D.S.; Chapman,D. G. (1961): Catch Evidence of a decline in beluga (Delphina- curves and mortality rates. Am. Fish. Soc, pterusleucas)abundanceoffWestGreenland. Trans.90, 181-189. ICESJ.MarineScience53;61-72. Sergeant, D.E. (1973): Biology of white whales Heide-J0rgensen, M.P. (1994): Distribution, ex- (Delphinapterus leucas) in Western Hudson ploitation and population Status of white Bay.J.Fish.Res.BoardCan.30, 1065-1090. whales (Delphinaterus leucas) and narwhals Stewart, R.E.A. (1994): Size-at-age relation- (Monodon monoceros) in West Greenland. ships as discriminators of white whale MeddrGr0nland,Biosci.39, 135-149. (Delphinapterus leucas) Stocks in the eastern HEIDE-J0RGENSEN, M.P.| JENSEN, J.; LARSEN, CanadianArctic.MeddrGr0nland,Biosci.39, A.H.; Teilmann J.; Neurohr, B. (1994): Age 217-225. estimation of white whales (Delphinapterus leucas) from Greenland. Meddr Gr0nland, Authors' addresses: Biosci.39, 187-193. M.P. Heide-J0rgensen, National Marine Mam- HEIDE-J0RGENSEN, M.P; Teilmann, J. (1994): mal Laboratory, 7600 Sand Point Way NE, Seat- Growth,reproduction,agestructureandfeed- tle, WA, USA (e-mail: madspeter.heide-joergen- ing habits of white whales (Delphinapterus [email protected]) and C. Lockyer, Danish Institute leucas) in West Greenland waters. Meddr for Fisheries Research, Charlottenlund Slot, Gr0nland,Biosci.39, 195-212. Charlottenlund, Denmark. Mamm. bioi. 66 (2001) 228-237 $St Mammalian Biology © Urban & FischerVerlag v http://www.urbanfischer.de/journals/mammbiol ^SfF Zeitschriftfür Säugetierkunde Original investigation A new species of Aepeomys Thomas, 1898 (Rodentia: Muridae) from the Andes of Venezuela ByJ. Ochoa G., MarisolAguilera, V. Pacheco, and P. J. Soriano Asociaciön Venezolana para La Conservaciön de Areas Naturales Caracas, Venezuela; Departamento de Estudios Ambientales, Universidad Simon Bolivar, Caracas, Venezuela; Department of Mammalogy, American Museum of NaturalHistory, NewYork, USA; Departamento de Biologia, Universidadde LosAndes, Merida,Venezuela. ReceiptofMs. 25. 04. 2000 AcceptanceofMs. 20. 09. 2000 Abstract A new species of Neotropical rodent of the genus Aepeomys is described based on 24 specimens collected in the Andean region ofVenezuela (Lara and Trujillo States). Among the diagnostic char- acters are: large size; firstand fifth digits ofpes notextending beyondthe commissure ofdigits 2- 3 and the first interphalangeal of digit four, respectively; posterior margin of zygomatic ramus of the maxilla with a distinctive notch; palate extending to the posterior border of M3 or behind this molar; and paraflexus of M1 and M2 divided by an enamel bridge. In addition, the new species shows the following karyological features: 22 chromosomal pairs (2n =44); 46 autosomal arms (FN =46); a low proportion oftwo-armed elements; automosal chromosomes with abundant hete- rochromatin around the pericentromeric areas; and short arms of chromosomes X and Y entirely heterochromatic. According to the most recent systematic revision ofthe species assigned to Aepe- omys, only two forms could be considered as members ofthis genus: A. lugens (the type species) and the taxon described herein. Both have geographic distributions restricted to highlands from the northern Andes, where the new species inhabits primary cloud forests and päramos located in the northeastern extreme ofthe Venezuelan Andean Cordillera. Key words: Aepeomys, Thomasomyine, Taxonomy, Andes, Venezuela Introduction Neotropical sigmodontine rodents of the Laverde et al. 1997; Musser and Carleton genus Aepeomys are members of the tho- 1993; Reig 1986; Voss 1993). After the ori- masomyine group, together with six addi- ginal description of Aepeomys by Thomas tional genera whose systematic and phylo- (1898), some authors have considered this genetic relationships remain unclear: taxon as a synonym of Thomasomys (e.g., Delomys Thomas, 1917; Phaenomys Tho- Cabrera 1961; Ellerman 1941; Handley mas, 1917; Rhagomys Thomas, 1917; Rhi- 1976). Nevertheless, the results of the most pidomys Tschudi, 1844; Thomasomys recent systematic revision of these Andean Coues, 1884; and Wilfredomys Avila-Pires, genera (Pacheco unpubl. data) and several 1960 (Aguilera et al. 1994, 2000; Gömez- previous publications (e.g.. Aguilera et al. 1616-5047/01/66/04-228 $15.00/0. Newspecies ofAepeomysfrom Venezuela 229 1994; Gardner and Patton 1976; Musser taciön Biolögica de Rancho Grande (EBRG), and Carleton 1993; Reig 1986; Soriano Maracay,Venezuela;theColecciöndeVertebrados and Ochoa 1997; Soriano et al. 1998) are delaUniversidadde LosAndes(CVULA),Meri- coincident in considering them as differen- da, Venezuela; and the Colecciön de Vertebrados delaUniversidadSimonBolfvar(CVUSB), Cara- tiated taxa. cas, Venezuela. Species, individuals and localities Four nominal species of Aepeomys have correspondingtothismaterialareasfollows:Aepe- been described (Cabrera 1961; Musser omysfuscatus (1; holotype). Colombia: Valle del and Carleton 1993), although at the pre- Cauca, San Antonio, near Cali, 2135m (AMNH- sent time only two of them are recognized 32230). Aepeomys lugens (21, including two topo- basutviaolnisdrteasxtari(cbtoetdhtohahvieghgleaongdrsapihnitchaelndoisrttrhi-- nteyjpoess,).2V4eknemzuWelaM-eMreirdiad,a2S9ta2t8e:mP(äArMamNoH-L9o6s16C9o;- ern Andes): Aepeomys lugens (Thomas, holotype of A. ottlevi); 5.5km E+2km S Tabay w1e89s6t)e,rnreVceonredezduelina steoverAanldleoacanlitEiecsuafdroorm; 21(50M5i27d00d)ml;e1(RkEemBfuRgNGi-o+1)5,25k72m160W0anmdMer(1i5E5dB7aR2)G(;-S1aEn5lt5a6M9Roorsarano)d,, andA.fuscatus (Allen, 1912), known from 9kmSSWMeridaCity,2160m(EBRG-22009and the western and central Andes of Colom- 22010; topotypes). Tachira State: Päramo Los Co- bia. However, the highly differentiated cra- lorados (Parque Nacional Päramos Batallön y La nial morphology shown by A.fuscatus with Negra), 12km SSE El Cobre, 3200m (EBRG- respect to A. lugens (the type species of 21513 to 21523; CVULA-5747, 5751, and 5753). the genus) and other related forms, has Aepeomys reigi (15). Venezuela-Lara State: El beenused among the arguments toconsider YBlaacnaqmubitüo,, 11670k0mmS(ECVSUaLnAar-e2,73P8a;rquEeBRGNa-c4i2o0n8a,l A.fuscatus as representative of a neglected 21735, 21440, and 22580to22582); RoadEl Blan- taxon whose evolutionary lineage could be quito-Sanare, km 6, Parque Nacional Yacambü, more related with the oryzomyine tribe, re- 1700m (EBRG-10621);ElAvileno,nearElBlan- presenting perhaps an undescribed genus quito, 9km SE Sanare, Parque Nacional (Yacam- (Pacheco and Voss unpubl. data). bü, 1600m (CVULA-2710 and 2718). Trujillo As part ofthe results ofa field study on the State: Macizo de Guaramacal, 9 kmESE Boconö, smallmammalcommunitiesinhabitinghigh- Parque Nacional Guaramacal, 3100m (CVULA- land ecosystems from the Andean region of 3350);Guaramacal,5kmEBoconö,ParqueNacio- Venezuela (Lara and Trujillo States), we TnaolrnGau,a7rakmmacEalB,oc2o2n3ö0,mPar(qCuVeULNaAc-i3o1n3a9l)G;uaPircaamLaa- caught a series of thomasomyine specimens cal,2300m(EBRG-22714);14to15kmETrujillo, whose general morphology corresponds to near Hacienda Misisi, 2225 to 2350m (EBRG- Ateerpnaelo,mcyrasni(asle,nasundstkraicrtyoo)l,oaglictahloufgehattuhreeisraerxe- n1e5z5u6e7laa:nd3515k5m68)S.+T2h2okmamsWomySsanhyClroipshtiolbuasl((5B).ueVnea- not referable to previously known species Vista), Tachira State, 2395m (EBRG-15597 to assigned to this genus. Apparently, they re- 15601). Thomasomys laniger (5) Venezuela: 4km present a new species that we describe be- S+6.5 kmETabay(LaCoromoto), MeridaState, low. Some ofthese specimens, in addition to T3a1b7a0ym(n(eEaBrRLGa-1C5or2o2m7ottoo)1,52M3e0)r;id5akSmtatSe,+372k5m1mE others collected in the Venezuelan Andes (EBRG-15231). Thomasomys vestitus. (1) Vene- and cited herein as representatives of the zuela: El Baho, 3km SE Santo Domingo, Merida newtaxon,wereformerlyrecordedasAepe- State,3010m(EBRG-32012). omys lugens or Aepeomys sp. by Handley Age criteriafollowVoss (1991). Cranialmeasure- (1976), Soriano et al. (1990), and Aguilera mentswere takenaccordingtoVoss (1988, 1991). et al. (1994, 2000). Nomenclature ofthe occlusal components ofmo- lar teeth follows Reig (1977). Karyological ana- lyses were carned out on 13 specimens of A. lu- gens and nine specimens representing the new Material and methods taxon(fivefromLaraState andfourfromTrujillo State), including the sample described by Agui- Specimens examined (all adults) are deposited in leraet al. (2000). Bone marrowmetaphase chro- the following institutions: American Museum of mosomes were obtained by a modification of NaturalHistory(AMNH);the ColecciöndelaEs- Ford and Hamerton's (1956) in vivo colchicine 230 OcHOAetaL technique. C- and G-banding patterns were ob- pelage, fused sphenoccipital suture, and the tained as described by Barros and Patton (1985) third molar erupted (age class IV). Col- manodsoCmheiarneolmleinceltatalu.re(19f72o)l,lorweesdpecLteivvealny. eCthroal-. gleucstted19b8y6 aMtaErlisBollanqAugiutiol,ePraarqeutealN.acinioAnua-l m(1a9l64a)r.mFnuunmdbaemresn.tal numbers (FN) are autoso- Yacambü, 17 km SE Sanare, Lara State,Ve- m nezuela, 1600 (approx. 9°40' N; 69°37'W; Fig. 1). Results Paratypes: Seven specimens (6 as dry skins Aepeomysreiginewspecies and skulls; one in alcohol) with karyotype analysis: Lara State, Parque Nacional Ya- Holotyoe: A female (dry skin, skull, and cambü, El Blanquito, 17 km SE Sanare, karyotype analysis; CVUSB-928) with adult 1600m; 3 males and 1 female collected by Newspecies ofAepeomysfrom Venezuela 231 M. Aguilera et al. (CVUSB-927, 1365, education and encouragement of many La- 1419, and 1420). Trujillo State, Parque Na- tin American mammalogists. cional Guaramacal (approx. 9°15'N; Distribution: Known only in highlands 70°12'W), Pica La Torna, 7 km E Boconö, (1600-3230m) from the northeastern ex- 2300m; 1 male and 2 females collected by treme of the Venezuelan Andes (Lara and J. Ochoa et al. (EBRG-22715 to 22717). Trujillo States). Etymology: The epithet reigi honors the Diagnosis: Size large for the genus as indi- memory of Dr. Oswaldo Reig, who de- cated by external andcranialmeasurements voted his life to the study ofthe systematics (Tab. 1), in addition to postcranial skeleton and evolution of South American rodents, development; first and fifth digits of pes and made important contributions to the not extendingbeyond the commissure ofdi- Table 1. Selected externaland cranial measurements (in millimeters) ofadult specimens ofAepeomys reigiand Aepeomystugens(ageclasses2-4)from Venezuela. Dataare: Mean±SD, (ränge), andsamplesize. 1Sampleincludestwotopotypesandthe holotypeofAepeomys(seespecimensexamined). Measurement A. reigi A. Lugens1 Lengthofheadand body 113.6±5.88 110.1±7.54 (104-125)15 (100-119)7 Lengthoftail 127.1±8.29 121.7+4.15 (116-142)15 (114-127)7 Lengthofhindfoot 27.9±1.30 27.0±3.96 (25-30)15 (20-30)7 Condylo-incisivelength 27.8±0.84 26.6±0.58 (26.6-29.3)16 (25.8-27.6)17 Lengthofdiastema 8.6±0.31 8.2±0.25 (8.0-9.0)18 (7.7-8.7)18 Lengthofmolars 4.5±0.11 4.3±0.12 (4.3-4.8)18 (4.0-4.4)18 Lengthofincisiveforamen 5.6±0.22 5.5±0.20 (5.2-6.0)16 (5.1-5.9)18 Breadthofincisiveforamen 2.4±0.18 2.3±0.14 (2.2-2.7)16 (2.0-2.5)18 Breadthofrostrum 5.0±0.23 4.5±0.27 (4.6-5.3)14 (4.0-5.1)16 Breadth ofpalatalbridge 3.8±0.16 3.5±0.25 (3.5-4.0)17 (3.0-4.0)17 Breadthofzygomaticplate 1.8±0.13 1.8±0.14 (1.6-2.1)18 (1.5-2.0)18 Leastinterorbitalbreadth 6.1±0.17 6.0±0.26 (5.9-6.4)17 (5.6-6.4)18 Breadth ofbraincase 13.3±0.22 13.1±0.35 (12.9-13.7)17 (12.4-13.8)18 Zygomaticbreadth 14.8±0.37 14.1±0.38 (14.2-15.6)15 (13.6-14.9)17 Depthofincisors 1.3±0.11 1.2±0.11 (1.0-1.4)17 (1.0-1.4)18 Lengthoforbitalfossa 9.1±0.24 8.4±0.21 (8.6-9.6)17 (8.0-8.8)17 232 OchoaetaL gits 2-3 and the first interphalangeal ofdig- averages approximately 50% of their re- it four, respectively; posterior margin of spective toothrows). Upper molars with zygomatic ramus of the maxilla with a dis- rounded protocone and hypocone, and the tinct notch; palate extending to the poster- paracone and metacone antero-posteriorly iorborderofM3 orbehind this molar; inter- sharp. Paraflexus of M1 and M2 divided by parietal length (along an antero-posterior an enamel bridge that crosses from the axis) near half of parietal length; and para- paracone tothe base ofthe anteroloph,pro- fiexus of M1 and M2 divided by an enamel ducing an internal fosseta. M3 with triangu- bridge that crosses from the paracone to lär shape in dorsal view. Mi with a distinc- the base of the anteroloph. Karyotype with tive protolophid in most specimens. which 22 chromosomal pairs (2n = 44), 46 autoso- reaches the cingulum. mal arms (FN = 46). a low proportion of Skull with general appearance resembling a two-armed elements, the automosal chro- typicalAepeomys (see Fig. 2 and 3 for com- mosomes with abundant heterochromatin parisons with A. lugens). Rostrum narrow around the pericentromeric areas, and the and elongated (approx. 1/3 of the greatest short arms of the chromosomes X and Y length of skull), with acute profile and only entirely heterochromatic. the external capsule of the nasolacrimal Description: Length of head and body 104- foramen exposed in dorsal view; nasal and 125 mm. Tail approximately as long as body premaxillary bones extending beyond the (Tab. 1), sparsely covered by short dark- anterior surface of incisors and the gnathic brown hairs and unicolored (dark above process to form a distinct rostral tube. Na- and below). Legs, heels, and dorsal surface sals laterally concave and flat in dorsal pro- of pes sparsely covered by brown hairs. file, forming a continuous surface with the Body pelage dense and soft (longer in spe- premaxillae; posterior border extending to cimens from the highest altitudes). Dorsal thelevelofthezygomaticplate. Interorbital coloration ranging from dark gray-brown constriction relatively broad« without con- to reddish gray-brown, with moderately to cealing (in dorsal view) the labial ridge of intensively hoary appearance. Dorsal für maxillary and the molars. Braincase moder- consisting of shorter hairs (approx. 9- ately inflated and slightly concave in dorsal 12 mm) with golden tips and scattered long- profile; the posterior surface concealing the er hairs (approx. 12-15 mm) with dark occipital condyles in dorsal view. Interpari- brown tips (in afewcaseswithwhitishtips); etal length (along an antero-posterior axis) both having the basal 75% gray. Ventral near half of parietal length. Lambdoidal pelage shorter (approx. 7 mm) and paler ridges scarcely developed. Zygomatic than dorsum. ranging from moderately to arches completely ossified. filamentous and intensively hoary (hairs with golden tips fragile. Zygomatic plate relatively narrow and the basal 75% gray). Pinnae 18-21 mm (Tab. 1; Fig. 3), with the posterior edge ex- long and furred on both sides: inside part tending to the first molar (Fig. 2). Posterior yellowish, contrasting in color with the dor- margin of zygomatic ramus of the maxilla sal für. Manus cream-colored and paler with a distinct notch. Lumen of the infraor- than hind feet. Pes narrow and long bital foramen compressed laterally and ex- (adapted for terrestrial life; Tab. 1); first panded dorso-ventrally. Gnathic process and fifth digits not extending beyond the scarcely developed. Masseteric tubercle commissure of digits 2-3 and the first inter- large. Palatal bridge moderately long pInhcailsaonrgseanlarorfodwigaitndfomuro,derresapteecltiyvedleyv.eloped b(Toarbd.er1;oFfigM. 32).orebxethenidnidngthitsomtohlearp.osPtoesrtieor-r (not robust), with sharp tips. Upper incisors iormargin ofpalate without medial process with the anterior surface slightly concave. in most specimens; therefore, the anterior Maxillary and mandibular toothrows margin of the mesopterygoid fossa has a relatively short (Tab. 1; Fig. 2); first shallow shape. Incisive foramina extending molars antero-posteriorly elongated (length posteriorly beyond the masseteric tubercle. Newspecies ofAepeomysfrom Venezuela 233 Fig. 2. Dorsaland ventralviews ofcrania ofAepeomys iugens (topotype; a, b), Aepeomysreigi(holotype; c, d), and Thomasomyslaninger(e, f).Approx.XI.9. withoutreachingthe level ofthe first molar; Comparisons: Among the thomasomine margins of the anterior half strongly con- group, the genus most closelyrelated toAe- vergent anteriorly. Postglenoid foramen peomys is believed to be Thomasomys compressed dorso-ventrally and expanded (Aguilera et al. 2000; Gardner and Pat- antero-posteriorly. Foramen magnum with ton 1976), whose cranial morphology is the inferior border almost reaching the lev- clearly differentiated from A. reigi and el of the auditory bulla. Auditory bulla A. Iugens in the following features (Fig. 2 moderately inflated. Mandible with the tip and 3): shorter rostrum; zygomatic arches of the condylar process behind the angular more expanded laterally; narrower interor- process. bitalregion; braincase lessinflated atthe le- Karyotype with 22chromosomal pairs vel oflambdoidal ridges; broaderzygomatic (2n=44), 46 autosomal arms (FN=46), plate; larger incisive foramina (almost and low proportion of two-armed elements reaching the first molars); and shorter pal- (Aguilera et al. 1994). Automosal chromo- ate (posterior border not extending beyond somes with abundant heterochromatin the third molar). In addition, Venezuelan around the pericentromeric areas. Short species of Thomasomys are larger (7^ aur- arms of chromosomes X and Y entirely eus, T hylophilus, and T. vestitus) and/or heterochromatic (Aguilera et al. 2000). have much paler brownish für (T. hylophi- 234 Ochoaetal. M a (near or before the posterior border of 3 in A. Iugens): posterior margin of palate without medial process in most specimens (therefore the anterior margin of the me- sopterygoid fossa is shallow rather than in- cipiently biconcave as in A. Iugens): maxil- M lary toothrow relatively longer; 3 larger and triangulär in dorsal view (rounded in A. Iugens); M1 and M2 with paraflexus di- vided by an enamel bridge (continuous in most specimens of A. Iugens): coronoid and condylar processes broader and larger. producing deeper sigmoid and angular notches. respectively. Mi with a distinctive protolophid in most specimens. which reaches the cingulum (reduced or absent in A. Iugens). Some ofthese features (particu- larly those related with cranial and dental morphology) show the maximun diver- gence in specimens of A. reigi from Lara State. In addition. A. Iugens has a very dif- ferent karyotype, with fewer chromosomal pairs (2n = 28 vs 2n = 44). more autosomal arms (FN = 48 vs FN =46), and a lower concentration of heterochromatin (espe- pFiogt.yp3e.;Laa)t,erAaelpveioemwyssofrecigrian(ihaoLooftAyepep;eobm),ysanidugTehnosm(atso-- caiuatlolysocmoanlspipaciurosusanindtthheeshYortcharrommsoosfomtew:o omyslaniger(c). Approx. XI.8. Aguilera et al. 1994, 2000). These chromo- somal variations were consistent when we Ins. T. vestitus and T. laninger) than Aepe- compared A. reigi with specimens ofA. Iu- omys Iugens andA. reigi. gens from two localities in Venezuela: the With respect to the species previously in- type locality (El Morro, Merida State) and cluded withinAepeomys.A. reigi resembles Päramo Los Colorados. Tächira State the external and cranial morphology of (Aguilera et al. 2000). A. Iugens, except for the following differ- Regarding A.fuscatus the external and cra- ences: size larger (Tab. 1): für on head and nial features ofthis species show a high de- body shorter and rougher: manus and pes gree of differentiation withA. reigi, reveal- broader; legs, heels. and dorsal surface of ing a morphological pattern that appears to pessparcelyhaired (denselyhairedinA. Iu- be taxonomically separated from the tho- gens): first and fifth digits of pes shorter; masomyine group and perhaps corresponds posterior margin ofzygomatic ramus ofthe to a taxon whose evolutionary lineage is maxilla with a distinct notch. rather than more relatedwith the oryzomyine tribe (Pa- shallow as in A. Iugens (as consequence. in checo and Voss unpubl. data). Among the A. reigi the orbital fossa is larger. Tab. 1): most conspicuous characteristics in A.fus- incisive foramina broader. with margins catus supporting this assessment are: darker showing a more convergent position ante- für coloration: shorter and broader rostrum riorly: interparietal longer in most speci- (without the acute profile shown byA. reigi mens (antero-posterior midline near halfof and A. Iugens): anterior portion of zygo- the parietal length, rather than 30^-0% as matic arches more expanded and broader: in A. Iugens): palate extending to the pos- broader zygomatic plate: narrower interor- terior border of 1VT or behind this molar bital breadth: braincase less inflated: short- Newspecies ofAepeomysfrom Venezuela 235 er incisive foramina and palate; and broad- with a primitive condition in eukariotic er mandibular branches. These features, in chromosomal evolution (Imai 1991). addition to the extremely high number of The geographic distribution of A. reigi chromosomal pairs (2n= 54) and autosomal seems to be allopatric with respect toA. lu- arms (FN = 62) reported by Gardner and gens, at least in the northeastern extreme of Patton (1976) for A.fuscatus are clear evi- the Venezuelan Andean Cordillera. How- dences of a differentiated evolutionary pat- ever, we donotrejectthe possibilityofsym- tern with respect toAepeomys. patric distribution in highlands (>1500m) near to the border of Merida and Trujillo States. Future karyological studies, in a Discussion more extensive area, are required to pro- vide a further diagnosis on the biogeo- The morphological Variation between graphic patterns of these taxa. Other non- A. reigi and A. lugens, in addition to the volant small mammals recorded at Yacam- high degree of differentiation in the num- bü and Guaramacal are: Coluromysphilan- ber and structure of chromosomes, support der, Didelphis albiventris, Didelphis marsu- the hypothesis of evolutionary divergences pialis, Gracilinanus dryas, Marmosops in both species, such as it has been pro- fuscatus, Micoureus demerarae, Cryptotis posed for other thomasomyine rodents meridensis, Mustela frenata, Sciurus grana- (Gardner and Patton 1976; Gömez-La- tensis, Heteromys anomalus, Akodon urichi, verde et al. 1997). Despite the higher di- Ichthyomys hydrobates, Microryzomys mi- ploid number in A. reigi with respect to nutus, Neacomys tenuipes, Oecomys flavi- A. lugens (44 vs 28), and based on their si- cans, Oligoryzomys fulvescens, Oryzomys milarities in fundamental numbers (46 vs meridensis, Rhipidomys venustus, Rhipid- 48, respectively), we postulate that karyolo- omys venezuelae and Thomasomys laninger gical differences found in these species (Soriano et al. 1990). could be reached by chromosomal rearran- TheknownecologicaldistributionofA. reigi gements evolving principally robertsonian correspondstoprimarycloudforests (humid changes (Aguilera et al. 2000). montane forest according to Huber and An important aspect within the evolution- Alarcön 1988) and small patches of pära- ary context of Aepeomys species, is the di- mos surrounded by continuous masses of rection of chromosomal transformation in cloud forests; these ecosystems, in addition A. reigi and A. lugens. According to Gard- toseasonalforestsandevergreendryforests, ner and Patton (1976), thomasomyine kar- have been previously recorded among the yotypes are characterized by a generalized ecological conditions used by A. lugens condition of diploid number of 42 or 44, in (Handley 1976; Sorianoet al. 1990).A. rei- addition to a predominantly acrocentric giappears to be arelativelyuncommonspe- autosomal complement. This generalized cies along its ecological ränge. Even though condition is present in A. reigi and allows field data for päramos are insufficient, sam- to consider it as a primitive form. This fact, plingeffortsof3724trap-nightsincloudfor- together with the great proportion of two- ests, accumulated during inventories con- armed elements shown by the karyotype of ducted by the authors, allowed to catch A. lugens, are arguments to postulate this 27individuals of A. reigi that represented last species as a derived form (Aguilera et 10.6% of total non-volant small mammals al. 2000). Some complementary evidences trappedinthisecosystem(Oryzomysalbigu- supporting this hypothesis are the differ- laris and Heteromys anomalus were the ences in quantity and distribution of the dominant species). Collected specimens constitutive heterochromatin: low and chro- have been found on the ground in densely mosomal restricted in A. lugens vs abun- forested sites (beside logs, at the base of dant and distributed in chromosomes of trees, in rocky places, along trails, or near A. regi; the last pattern has been associated smallstreams) orin open areas (close to the